TM the King and Queen of Bhutan will be visiting Japan from November 15-19 on the invitation of the Japanese emperor to commemorate 25th anniversary of Bhutan-Japan diplomatic relations..
It will be first state visit of Bhutanese monarch to Japan ever.

Programm of the visit:

1. HM the King will address to DIET on November 17th;
2. HM the King will meet the Crown Prince and the PM (the Emperor will not be able to attend - Source);
3. HM the King will reaffirm the goodwill and friendship of the Bhutanese people towards the people of Japan, and express solidarity with the victims of the earthquake of March 11th, 2011.4.The Keio University will confer on HM the King an honorary doctorate in economics, where HM will deliver an acceptance lecture to the students and faculty.
5. The state banquet will be hosted by Imperial family (the Emperor will not be able to attend).

The king and queen of Bhutan, who are visiting Japan as state guests, expressed their condolences for the victims of the March 11 earthquake and tsunami during a meeting with Prime Minister Yoshihiko Noda and his wife on Tuesday, the Foreign Ministry said.

Thanks for the updates !
I assume that the lack of tiaras can be attributed to the fact that the Bhutanese reigning couple prefers to wear the traditional clothing. The Japanese side has decided to go with the traditional theme. Hence Princess Kiko and other ladies attending the banquet wore kimonos.

__________________"I never did mind about the little things"
Amanda, "Point of No Return"

kuenselonline » Blog Archive » Our people share a special bond: His Majesty
The people of Bhutan and Japan share a special bond, His Majesty the King said at the state banquet hosted by the Emperor and Empress of Japan yesterday evening.
His Majesty conveyed the prayers and good wishes of the fourth Druk Gyalpo to the Imperial family and acknowledged their pivotal roles in furthering the friendship between the two countries.
“Personally, I have to say that it is a special honour and happiness being here on the invitation of Their Majesties so soon after our wedding,” His Majesty said. “It is to Their Majesties that Jetsun and I will always look for inspiration and guidance during the course of our life together, and as we serve our nation.”